Organic electroluminescent device with SiN layer containing hydrogen and fluorine

ABSTRACT

An organic EL device includes a substrate; a layered structure including a first electrode, an organic layer, and a second electrode disposed on the substrate in this order; and laminated protective layers surrounding at least the layered structure. The protective layers are composed of silicon, nitrogen, hydrogen, and fluorine. The fluorine content in the outermost protective layer is in the range of 0.01 to 1.0 atomic percent.

This application is a divisional application of U.S. application Ser.No. 11/611,352 filed Dec. 15, 2006, which claims priority of JapanesePatent Application Nos. 2005-370091, filed Dec. 22, 2005 and2006-305240, filed Nov. 10, 2006. The contents of all of theaforementioned applications are hereby incorporated by reference hereinin their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electroluminescent (EL)device for use in emissive displays, surface-emitting light sources, andthe like.

2. Description of the Related Art

In recent years, organic EL devices have actively been developed. Thus,technologies regarding protective layers for blocking the intrusion ofmoisture and oxygen from the outside have also been studied to make fulluse of their luminescence properties. Protective layers need to not onlyblock the intrusion of moisture and oxygen, but also have excellentoptical properties from the viewpoint of luminescence.

Japanese Patent Laid-Open No. 11-242994 discloses a silicon nitrideprotective layer formed by plasma chemical vapor deposition (CVD) atroom temperature.

In protective layers formed of silicon nitride, there is a trade-offbetween the optical properties and the protective performance.Specifically, the silicon nitride protective layer just formed by plasmaCVD as described in the patent document exhibits higher lightabsorption, as well as high protective performance. Thus, although thesilicon nitride protective layer has a small deterioration rate ofoptical properties in an endurance test, its initial optical propertiesare poor. Hence, the silicon nitride protective layer hardly makes fulluse of high luminous efficiencies of recent organic ELs.

SUMMARY OF THE INVENTION

The present invention provides an organic EL device that includes aprotective layer functioning as an excellent protective film andexhibiting excellent optical performance.

A first aspect of the present invention provides an organic EL devicethat includes

-   -   a substrate;    -   a layered structure including a first electrode, an organic        layer, and a second electrode disposed on the substrate in this        order, and    -   laminated protective layers disposed closer to a light        extraction side than the second electrode;    -   wherein the protective layers are composed of silicon, nitrogen,        hydrogen, and fluorine, and    -   each protective layer contains 0.01 to 1 atomic percent of        fluorine.

A second aspect of the present invention provides an organic EL devicethat includes

-   -   a substrate;    -   a layered structure including a first electrode, an organic        layer, and a second electrode disposed on the substrate in this        order, and    -   laminated protective layers disposed closer to a light        extraction side than the second electrode;    -   wherein the protective layers include    -   a first protective layer disposed on the substrate side, the        first protective layer being composed of silicon, oxygen,        hydrogen, and fluorine and being free of nitrogen, and    -   a second protective layer disposed on the light extraction side,        the second protective layer being composed of silicon, nitrogen,        hydrogen, and fluorine,    -   wherein the first protective layer contains 0.01 to 4 atomic        percent of fluorine, and    -   the second protective layer contains 0.01 to 1 atomic percent of        fluorine.

The fluorine content in the laminated protective layers according to thefirst aspect or the second aspect may decrease in a direction from thesubstrate side toward the light extraction side.

As described above, the present invention provides an organic EL devicethat includes a protective layer disposed on a light extraction side ofa second electrode. The protective layer can maintains excellentluminescence properties of the organic EL device even under hightemperature and high humidity and has excellent initial properties.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a layered structure of anorganic EL device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a layered structure of an organic ELdevice according to another embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

The present invention is described in detail below with reference toFIG. 1. However, it is to be understood that the present invention isnot limited to an organic EL device illustrated in FIG. 1.

In the present embodiment, one of electrodes of an organic EL device isconnected to a switching element, for example, a thin-film transistor(TFT), which controls the luminescence.

A plurality of organic EL devices according to the present embodimentmay separately be placed on the same plane. Such organic EL devices canbe utilized as picture elements of a display panel. Furthermore, anorganic EL device according to the present invention can be used as amono-color light-emitting apparatus. Alternatively, a plurality oforganic EL devices according to the present invention can be used as afull-color light-emitting apparatus, in which the organic EL devicesemit different colors.

FIG. 1 illustrates a schematic cross-sectional view of an organic ELdevice according to an embodiment of the present invention. This organicEL device includes a glass substrate 11, a first electrode 12, anorganic layer 13, a second electrode 14, a first protective layer 15-1,and a second protective layer 15-2.

An organic EL device according to the present invention essentiallyincludes the first electrode 12, the organic layer 13, and the secondelectrode 14, and may further include the first protective layer 15-1and the second protective layer 15-2 disposed on the second electrode14, and may still further include a packed layer and a sealing substrate(both not shown). The organic layer 13 is composed of at least onesublayer. In addition to a luminescent sublayer, the organic layer 13may include a positive hole transport sublayer, a positive holeinjection sublayer, an electron transport sublayer, an electroninjection sublayer, and/or a carrier-blocking sublayer. Alternatively,at least two of these sublayers may be combined to function as aluminescent sublayer.

The second electrode 14 is formed of a transparent electroconductivefilm of low resistance, such as indium tin oxide (ITO) or indium oxide(In₂O₃). The first electrode 12 is a reflecting anode that can have alarge work function. For example, gold (Au), platinum (Pt), chromium(Cr), palladium (Pd), selenium (Se), iridium (Ir), copper iodide, or analloy may be used.

Such a structure in which the substrate is closer to the reflectingelectrode than the transparent electrode is referred to as a topemission structure. In the top emission structure, light emitted fromthe luminescent sublayer is extracted from the top of the organic ELdevice.

In the top emission structure, the protective layers 15-1 and 15-2, thepacked layer, and the sealing substrate (both not shown) should betransparent to light emitted from the luminescent sublayer to send outthe light without significant loss. The protective layers 15-1 and 15-2,the packed layer, and the sealing substrate according to the presentembodiment are formed of colorless transparent materials. In addition, acircularly polarizing plate (for example, a composite polarizer of alinearly polarizing plate and a retardation plate, such as a λ/4 plate)may be attached directly to the top of the protective layer 15-2.

A protective layer according to one embodiment of the present inventionis described below.

The protective layers 15-1 and 15-2 are inorganic films composed ofsilicon, nitrogen, and hydrogen and contain fluorine (F). Fluorine mayreduce structural defects in the protective layers 15-1 and 15-2, thoughthe reason for this is not clear.

The structural defects are associated with the structures of theprotective layers. Specifically, because each protective layer is formedof an amorphous material, the interatomic distances are not uniform andvary locally. An amorphous material may grow differently in a mannerthat depends on the state of the growth surface. The amorphous materialmay therefore locally have a higher internal stress. The locally higherinternal stress may cause microscopical detachment of the organic layer,which results in an image defect.

Heretofore, to reduce such defects, the thickness of a protective layermay be increased to block the detachment, though this causes an increasein cost. Alternatively, a protective layer having high protectiveperformance may be used while the optical properties are not a littlecompromised. However, these countermeasures have insufficient effects.

The present invention incorporates more effective fluorine into aprotective layer. Fluorine can activate the surface reaction during filmformation. In addition, strong bonding between fluorine and other atomsallows the protective layer to be structurally stable, uniform, and lessdefective even when a protective layer is formed at low temperature(room temperature). Such beneficial effects can be achieved when thefluorine content in a protective layer is at least 0.01 atomic percent.

However, an increase in the fluorine content may cause an increase inhygroscopicity. Actually, when the fluorine content in a protectivelayer exceeds 1.0 atomic percent, a fracture or detachment in theprotective layer probably due to expansion of the protective layer isobserved and may cause a deterioration in protective performance. Hence,the fluorine contents in the first protective layer 15-1 and the secondprotective layer 15-2 can be in the range of 0.01 to 1.0 atomic percentof the total constituent atoms.

In addition, even when the fluorine contents in the protective layersare within this range, not a little moisture absorption is caused byfluorine. A region in the vicinity of the top surface of the protectivelayers can therefore contain less fluorine. In other words, the fluorinecontent can decrease in a direction from the substrate side toward thelight extraction side in a continuous or stepwise manner.

When the fluorine contents in the protective layers are within the rangedescribed above, the optical properties of the protective layer remainunchanged. Hence, when fluorine is added to a protective film havingoptical properties designed for a raw material gas containing, forexample, silicon and nitrogen to improve the protective characteristics,the optical properties and the protective characteristics canindependently be controlled. This increases flexibility in determiningthe ratio of major elements, that is, silicon, nitrogen, and hydrogen,of the protective layer.

An objective of providing the laminated protective layers is to blockintrusion path of moisture and oxygen from the outside. Thus, when theintrusion path occurs in the protective layer 15-1, the film formationmay temporarily be stopped after the protective layer 15-1 is formed.Then, the protective layer 15-2 may be formed under differentconditions. Alternatively, the formulations of the protective layers15-1 and 15-2 may continuously be changed to block the intrusion pathwithout stopping the film formation. For example, the fluorine contentin the protective layer 15-1 can be greater than the fluorine content inthe protective layer 15-2.

The compositions of the protective layers can be in the following range,as determined by a Rutherford scattering spectrum (RBS) method. The RBSmethod can analyze the composition in the depth direction.

The protective layer 15-2 can contain 29 to 40 atomic percent of siliconand 36 to 50 atomic percent of nitrogen. The ratio of nitrogen tosilicon can be 1.0 to 1.43.

The protective layer 15-1 can contain 10 to 50 atomic percent ofhydrogen.

The protective layers 15-1 and 15-2 contain no detectable oxygen (aboutless than 1 atomic percent).

A protective layer according to another embodiment of the presentinvention is described below.

The protective layer 15-1 is an inorganic film composed of silicon,oxygen, and hydrogen and is free of nitrogen. The protective layer 15-1contains fluorine (F). The protective layer 15-2 is an inorganic filmcomposed of silicon, nitrogen, and hydrogen and contains fluorine (F).

Fluorine in the protective layers has the effects as described above.The relationship between the fluorine content in a protective layer andthe protective performance depends on the composition of the protectivelayer. The protective layer 15-1 can have excellent protectiveperformance when the fluorine content is in the range of 0.01 to 4.0atomic percent of the total constituent atoms.

When the fluorine content in the protective layer 15-1 is within thisrange, its optical properties remain unchanged, as described above.Hence, when fluorine is added to a protective film having opticalproperties designed for a raw material gas containing silicon and oxygento improve the protective characteristics, the optical properties andthe protective characteristics can independently be controlled.

In particular, different optical designs can be applied to theprotective layer 15-1 composed of silicon, oxygen, and hydrogen and freeof nitrogen and to the protective layer 15-1 composed of silicon,nitrogen, and hydrogen. Depending on the performance required for theorganic EL device, each protective layer can appropriately be designed.In general, a protective layer composed of silicon, oxygen, and hydrogenand free of nitrogen exhibits lower light absorption and has a lowerrefractive index than those of a protective layer composed of silicon,nitrogen, and hydrogen.

As described above, an objective of providing the laminated protectivelayers is to block intrusion path of moisture and oxygen from theoutside. Lamination of the protective layer 15-1 and the protectivelayer 15-2 having different compositions is therefore more effective.

The compositions of the protective layers can be in the following range,as determined by a Rutherford scattering spectrum (RBS) method.

The composition of the protective layer 15-2 is in the range describedabove.

The protective layer 15-1 can contain 20 to 40 atomic percent of siliconand 40 to 80 atomic percent of oxygen. The ratio of oxygen to siliconcan be 1.5 to 2.5. The protective layer 15-1 can contain 10 to 50 atomicpercent of hydrogen. The protective layer 15-1 contains no detectablenitrogen (about less than 1 atomic percent).

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions.

EXAMPLES Reference Example

First, a protective monolayer was evaluated.

[Formation of Protective Monolayer on Glass Substrate]

An electron injection sublayer having a predetermined thickness amongorganic sublayers used in the following examples was deposited on aglass substrate having a thickness of 0.8 mm. Then, ITO was deposited onthe electron injection sublayer by sputtering to form a transparentelectrode layer having a thickness of 100 nm. Then, a protectivemonolayer composed of silicon, nitrogen, hydrogen, and fluorine wasformed in the following manner.

A film-forming apparatus is a plasma CVD apparatus utilizing highfrequency power. High frequency power is applied to a raw material gasflowing through parallel-plate electrodes to generate glow discharge. Aprotective layer is formed on the glass substrate.

A SiH₄ gas, a SiF₄ gas, and a N₂ gas were introduced at various ratiosat a pressure of 100 Pa and at room temperature without heating thesubstrate. The power applied to the electrodes was 5 to 100 W.

The fluorine content was varied between 0.001 and 2.0 atomic percent bychanging the composition of the raw material gas and other conditions.

[Evaluation of Protective Monolayer Formed on Glass Substrate]

The protective monolayer formed on the glass substrate was evaluated asfollows.

(1) Cross-cut Test

Vertical and horizontal cuts each having a length of 20 mm at 1 mmspacing were made on a predetermined region of a protective monolayercontaining fluorine as shown in Table 1. A cellophane adhesive tape wasattached to the region so that all the 1 mm² cut squares were inintimate contact with the tape. Then, the tape was peeled at an angle of180° according to an ASTM specification. The area of the protectivemonolayer peeled together with the tape was measured. The protectivemonolayer was not peeled off by one peeling test. Thus, a plurality ofpeeling tests was performed. Table 1 shows the results. The peeled areais indicative of the adhesiveness of the protective film. A largerpeeled area indicates poorer adhesion. Table 1 shows the reciprocal ofthe peeled area as a measure of the adhesiveness, normalized to thevalue of a protective film containing 0.01 atomic percent of fluorine(reference example 1-2). A lower relative value indicates pooreradhesion.

(2) Evaluation of Moisture Barrier Property

The moisture barrier property was determined with a glass substrate onwhich metallic calcium was deposited. A glass substrate was placed in adeposition apparatus, in which the glass substrate can be conveyed invacuo between a protective layer-forming chamber (CVD) and a metalcalcium deposition chamber. Calcium was evaporated onto the glasssubstrate at a predetermined thickness. A protective layer containingfluorine as shown in Table 1 was formed on the metal calcium. Thisspecimen was placed in an atmosphere of 100% RH at 121° C. and 0.2 MPafor 100 hours. Then, the light transmittance of the specimen wasmeasured. Moisture passing through the protective layer reacted withcalcium to yield calcium hydroxide. The relationship between the lighttransmittance and the fluorine content was examined. While calciumexhibits low optical transparency, calcium hydroxide exhibits highoptical transparency.

Thus, the light transmittance is indicative of the moisture barrierproperty of the protective film. A larger light transmittance indicatesa poorer moisture barrier property. Table 1 shows the reciprocal of thelight transmittance as a measure of the moisture barrier property,normalized to the value of the protective film containing 0.01 atomicpercent of fluorine (reference example 1-2). A lower relative valueindicates a poorer moisture barrier property.

TABLE 1 Moisture barrier Fluorine content Cross-cut test property SampleNo. (atomic %) (relative value) (relative value) Reference 0.005 0.770.79 example 1-1 Reference 0.01 1.00 1.00 example 1-2 Reference 0.1 1.030.97 example 1-3 Reference 1.0 1.05 0.96 example 1-4 Reference 1.2 0.970.88 example 1-5 Reference 2.0 0.98 0.89 example 1-6

As seen in Table 1, when the fluorine content in the protective layer isin the range of 0.01 to 2.0 atomic percent, detachment, for example,caused by internal stress did not occur in the protective layer and alsoin the underlying organic layer and the cathode layer. When the fluorinecontent in the protective layer is in the range of 0.01 to 1.0 atomicpercent, the protective layer exhibited an excellent moisture barrierproperty.

An organic EL device according to the present invention is furtherdescribed in the following examples. However, the present invention isnot limited to these examples.

Example 1

FIG. 2 illustrates an organic EL device including protective layersformed in the same way as that in the reference example. The organic ELdevice includes a glass substrate 21, a TFT circuit 22, a deviceisolation film 23, a first electrode 24, an organic layer 25, a secondelectrode 26, a first protective layer 27, a second protective layer 28,and a polarizer 29. The TFT circuit 22 was formed on the glass substrate21 having a thickness of 0.7 mm. The first electrode 24 composed ofchromium was formed on the TFT circuit 22. Then, a polyimide isolationfilm 23 was formed to produce a device substrate. The organic layer 25was formed on the chromium electrode 24 of the device substrate. Theorganic layer 25 included a hole transport sublayer, a luminescentsublayer, an electron transport sublayer, and an electron injectionsublayer laminated from the bottom to the top. Then, ITO was depositedon the organic layer by sputtering to form a transparent electrode layer26 having a thickness of 100 nm.

[Formation of Protective Layer]

The specimen was conveyed to another film-forming chamber. The firstprotective layer 27 composed of silicon, nitrogen, hydrogen, andfluorine was formed on the second electrode 26, as described in thereference example. The first protective layer 27 had a thickness of 2μm. The fluorine content in the first protective layer 27 was adjustedto 1.0 atomic percent by controlling the composition of a raw materialgas.

After the film formation was temporarily stopped, the second protectivelayer 28 containing fluorine as shown in Table 2 was formed on the firstprotective layer 27 in the same way as the first protective layer 27.The second protective layer 28 had a thickness of 1 μm. While thecontents of silicon, nitrogen, and hydrogen in the second protectivelayer 28 varied with the adjustment of the fluorine content, they werewithin the range described above.

Furthermore, as in the reference example, each element content in thedeposited films was held constant.

The organic EL device thus formed was connected to a driving powersupply at the first electrode 24 and the second electrode 26. Theluminous efficiency of the organic EL device was determined. Anadditional specimen was prepared in the same way as the specimen for theevaluation of luminous efficiency. Two analyses were performed tomeasure the fluorine content in a protective layer and to determine afluorine-rich region and a fluorine-poor region. A Rutherford scatteringspectrum (RBS) analysis and a resonant nuclear reaction analysis (NRA)were performed.

[Evaluation of Organic EL Device]

The luminance of an organic EL device was measured at a constantelectric current before and after an endurance test under hightemperature and high humidity. The luminous area after an endurance testunder high temperature and high humidity varied with the conditionsunder which a protective film was formed. Since the luminance may beproportional to the luminous area, the luminance was regarded as theevaluation criterion for the luminescence properties.

An organic EL device including the second protective layer 28 containingfluorine as shown in Table 2 was subjected to an endurance test underhigh temperature and high humidity. Specifically, an organic EL devicewas placed in an atmosphere of 90% RH at 60° C. for 1000 hours. Thedeterioration rate was calculated from the luminances before and afterthe endurance test. Table 2 shows the deterioration rate together withthe initial luminance.

When the second protective layer 28 composed of silicon, nitrogen, andhydrogen contained 0.01 to 1.0 atomic percent of fluorine according tothe present invention, deterioration in luminance under high temperatureand high humidity was reduced, and no dark spot was observed. Theresults demonstrated that an organic EL device according to the presentinvention exhibited high stability. In addition, when the secondprotective layer 28 contained 0.01 to 1.0 atomic percent of fluorine,the organic EL device had high initial luminance.

TABLE 2 Fluorine Deterioration Fluorine content content in rate inInitial in first second endurance luminance protective layer protectivelayer test (relative (relative Overall Sample No. (atomic %) (atomic %)value) value) rating Comparative 1.0 0.005 79.0 0.91 Poor exampleExample 1-1 0.01 100.0 1.00 Excellent Example 1-2 0.1 100.0 1.01Excellent Example 1-3 1.0 97.0 1.02 Good Comparative 1.2 81.5 0.84 Poorexample Comparative 2.0 79.5 0.74 Poor example Deterioration rates inendurance test and Initial luminances are relative values normalized tothe values of Example 1-1.

Example 2

A specimen including a glass substrate 21, a TFT circuit 22, a deviceisolation film 23, a first electrode 24, an organic layer 25, and asecond electrode 26 was formed in the same way as in Example 1.

The specimen was conveyed to another film-forming chamber. A firstprotective layer 27 composed of silicon, nitrogen, hydrogen, andfluorine was formed on the second electrode 26, as described inExample 1. The first protective layer 27 had a thickness of 2 μm. Thefluorine content in the first protective layer 27 was adjusted to thevalue shown in Table 3 by controlling the film-forming conditions. As inExample 2, while the contents of silicon, nitrogen, and hydrogen in thefirst protective layer 27 varied with the adjustment of the fluorinecontent, they were within the range described above.

After the film formation was temporarily stopped, a second protectivelayer 28 containing fluorine as shown in Table 3 was formed on the firstprotective layer 27 in the same way as the first protective layer 27.The second protective layer 28 had a thickness of 1 μm.

Furthermore, as in Example 1, each element content in the protectivelayers 27 and 28 was held constant.

The organic EL device thus formed was connected to a driving powersupply at the first electrode 24 and the second electrode 26. Theluminous efficiency of the organic EL device was determined. Anadditional specimen was prepared in the same way as the specimen for theevaluation of luminous efficiency, and the fluorine contents in theprotective layers were measured, as in Example 1.

[Evaluation of Organic EL Device]

As described above, the luminescence properties of the organic EL devicethus formed were determined before and after an endurance test underhigh temperature and high humidity.

An organic EL device including the first protective layer containingfluorine as shown in Table 3 was subjected to an endurance test in anatmosphere of 90% RH at 60° C. for 1000 hours, as in Example 1. Theluminescence properties were determined after the endurance test. Table3 shows the results. An organic EL device that includes the firstprotective layer and the second protective layer both manufactured underthe same conditions was fixed on a metal plate and was dropped from aheight of 70 cm (drop impact of about 10 G). After the drop impact testwas performed twice, the organic EL device was subjected to an endurancetest in an atmosphere of 90% RH at 60° C. for 250 hours. Theluminescence properties were determined after the endurance test. Table3 shows the results.

When the first protective layer composed of silicon, nitrogen, andhydrogen contained 0.01 to 1.0 atomic percent of fluorine according tothe present invention, deterioration in luminance under high temperatureand high humidity was reduced, and no dark spot was observed. Theresults demonstrated that an organic EL device according to the presentinvention exhibited high stability. When the fluorine content wasgreater than 1.0 atomic percent, a dark spot probably caused by afracture of the first protective layer was observed. When the firstprotective layer contained 0.01 to 1.0 atomic percent of fluorineaccording to the present invention, the first protective layer showedless deterioration in protective performance under high temperature andhigh humidity and was resistant to a physical impact. The resultsdemonstrated that an organic EL device including the first protectivelayer according to the present invention exhibited high stability.

TABLE 3 Fluorine Deterioration content in first Fluorine content rate inLuminance after protective in second endurance endurance test layerprotective layer test (relative and drop impact Sample No. (atomic %)(atomic %) value) test (relative value) Comparative 0.005 0.1 80.0 85.5example Comparative 0.08 81.0 86.0 example Example 2-1 0.01 98.5 98.5Example 2-2 0.1 99.0 99.5 Example 2-3 0.6 99.5 98.5 Example 2-4 1.0100.0 100.0 Comparative 1.2 85.0 85.5 example Deterioration rates inendurance test and Luminances after endurance test and drop impact testare relative values normalized to the values of Example 2-4.

Example 3

A specimen including a glass substrate 21, a TFT circuit 22, a deviceisolation film 23, a first electrode 24, an organic layer 25, and asecond electrode 26 was formed in the same way as in Example 2.

Then, the specimen was conveyed to another film-forming chamber. A firstprotective layer 27 composed of silicon, oxygen, hydrogen, and fluorineand free of nitrogen was formed on the second electrode 26. The firstprotective layer 27 had a thickness of 1.5 μm. The fluorine content inthe first protective layer 27 was adjusted to the value shown in Table 4by controlling the film-forming conditions. As in Example 2, while thecontents of silicon, oxygen, and hydrogen in the first protective layer27 varied with the adjustment of the fluorine content, they were withinthe range described above.

After the film formation was temporarily stopped, a raw material gas waschanged. Then, a second protective layer 28 composed of silicon,nitrogen, and hydrogen and containing fluorine as shown in Table 4 wasformed on the first protective layer 27. The second protective layer 28had a thickness of 1 μm. As in Example 2, each element content in theprotective layers 27 and 28 was held constant.

As in Example 2, the luminous efficiency of the organic EL device thusformed was determined. An additional specimen was prepared in the sameway as the specimen for the evaluation of luminous efficiency, and thefluorine contents in the protective layers were measured, as in Example1.

[Evaluation of Organic EL Device]

As described above, the luminescence properties of the organic EL devicethus formed were determined before and after an endurance test underhigh temperature and high humidity.

The organic EL device was subjected to an endurance test in anatmosphere of 90% RH at 60° C. for 1000 hours, as in Example 2. Theluminescence properties were determined after the endurance test. Table4 shows the results.

When the first protective layer composed of silicon, oxygen, andhydrogen and free of nitrogen contained 0.01 to 4.0 atomic percent offluorine according to the present invention, deterioration in luminanceunder high temperature and high humidity was reduced, and no dark spotwas observed. The results demonstrated that an organic EL deviceaccording to the present invention exhibited high stability.

TABLE 4 Fluorine Fluorine content in Deterioration content in firstsecond rate in protective layer protective layer endurance test SampleNo. (atomic %) (atomic %) (relative value) Example 3-1 0.005 1.0 85.0Example 3-2 0.08 88. Example 3-3 0.01 99.5 Example 3-4 0.1 98.5 Example3-5 1.0 100.0 Example 3-6 2.0 99.0 Example 3-7 4.0 98.5 Example 3-8 4.590.0 Deterioration rates in endurance test are relative valuesnormalized to the values of Example 3-5.

Example 4

A specimen including a glass substrate 21, a TFT circuit 22, a deviceisolation film 23, a first electrode 24, an organic layer 25, and asecond electrode 26 was formed in the same way as in Example 1.

As in Example 1, a first protective layer 27 composed of silicon,nitrogen, hydrogen, and fluorine was formed on the second electrode 26.The first protective layer 27 had a thickness of 2 μm. The fluorinecontent in the first protective layer 27 was gradually changed in adirection from the substrate side toward the display side of the organicEL device, as shown in Table 5. After the film formation was temporarilystopped, a second protective layer 28 having a varied fluorine contentshown in Table 5 was formed on the first protective layer 27. The secondprotective layer 28 had a thickness of 1 μm.

As in Example 1, while the contents of silicon, nitrogen, and hydrogenin the first protective layer 27 varied with the adjustment of thefluorine content, they were within the range described above.

The organic EL device thus formed was connected to a driving powersupply at the first electrode 24 and the second electrode 26. Theluminous efficiency of the organic EL device was determined. Anadditional specimen was prepared in the same way as the specimen for theevaluation of luminous efficiency, and the fluorine contents in theprotective layers were measured, as in Example 1.

[Evaluation of Organic EL Device]

As described above, the luminescence properties of the organic EL devicethus formed were determined before and after an endurance test underhigh temperature and high humidity.

An organic EL device including the protective layers having fluorinecontents shown in Table 5 was subjected to an endurance test in anatmosphere of 90% RH at 60° C. for 1000 hours, as in Example 1. Theluminescence properties were determined before and after the endurancetest. Table 5 shows the results.

The results demonstrated that an organic EL device according to thepresent invention, in which a first protective layer and a secondprotective layer are laminated, and the fluorine content in eachprotective layer is in the range of 0.01 to 1.0 atomic percent anddecreases in a direction from the substrate side toward the displayside, showed less deterioration in protective performance under hightemperature and high humidity and thereby exhibited high stability. Thecontinuously varied fluorine content gave excellent results.

TABLE 5 Deterioration Fluorine content Fluorine content in rate in infirst protective second protective endurance test Sample No. layer(atomic %) layer (atomic %) (relative value) Example 4-1 1.0-0.6 0.5-0.01 100.0 Example 4-2 0.5-0.1 0.09-0.01 99.0 Example 4-3 1.0-0.50.5-0.1 100.0 Example 4-4 1.0 0.1 98.0 Comparative 2.0-0.5 0.5-0.1 88.0example Comparative 1.0-0.5 0.5-0.0 87.0 example Deterioration rates inendurance test are relative values normalized to the values of Example4-1.

Example 5

A specimen including a glass substrate 21, a TFT circuit 22, a deviceisolation film 23, a first electrode 24, an organic layer 25, and asecond electrode 26 was formed in the same way as in Example 3.

As in Example 3, a first protective layer 27 composed of silicon,nitrogen, hydrogen, and fluorine was formed on the second electrode 26.The first protective layer 27 had a thickness of 3 μm. The fluorinecontent in the first protective layer 27 was adjusted to the value shownin Table 6 by controlling the film-forming conditions.

In Examples 5-1, 5-2, and 5-3, after the formation of the firstprotective layer 27, the film-forming conditions were gradually changedto form a second protective layer 28 containing fluorine as shown inTable 6 under continuous discharge. In Examples 5-4 and 5-5, after thefirst protective layer was formed, the film formation was temporarilystopped. Then, the second protective layer was laminated.

As in Example 3, while the contents of silicon, nitrogen, and hydrogenin the protective layers varied with the adjustment of the fluorinecontent, they were within the range described above.

The luminous efficiency of an organic EL device including the protectivelayers was determined, as in Example 3. An additional specimen wasprepared in the same way as the specimen for the evaluation of luminousefficiency, and the fluorine contents in the protective layers weremeasured, as in Example 3.

[Evaluation of Organic EL Device]

As described above, the luminescence properties of the organic EL devicethus formed were determined before and after an endurance test underhigh temperature and high humidity.

As seen in FIG. 6, the organic EL devices according to Examples 5-1 to5-5 exhibited excellent performance. Specifically, when the firstprotective layer and the second protective layer are laminated and thefluorine content in each protective layer is in the range of 0.01 to 1.0atomic percent, the organic EL device showed less deterioration inluminescence properties under high temperature and high humidity andthereby exhibited high stability.

Furthermore, the organic EL devices according to Examples 5-1 to 5-3, inwhich the first protective layer and the second protective layer werecontinuously formed, had almost the same deterioration rates andexhibited high stability.

TABLE 6 Fluorine Fluorine content Continuity Deterioration content infirst in second between first rate in protective layer protective layerand second endurance test Sample No. (atomic %) (atomic %) protectivelayers (relative value) Example 5-1 1.0 0.5 continuous 100.0 Example 5-20.5 0.1 continuous 99.5 Example 5-3 0.5 0.01 continuous 99.0 Example 5-41.0 0.5 discontinuous 99.5 Example 5-5 0.5 0.1 discontinuous 99.0Deterioration rates in endurance test are relative values normalized tothe values of Example 5-1.

This application claims the benefit of Japanese Application No.2005-370091 filed Dec. 22, 2005, which is hereby incorporated byreference herein in its entirety.

1. A top emission organic electroluminescent device comprising: asubstrate; a layered structure including a first electrode, an organiclayer, and a second electrode disposed on the substrate in this order,and a SiN layer disposed closer to a light extraction side than thesecond electrode; wherein the SiN layer contains 10 to 50 atomic percentof hydrogen and 0.01 to 1 atomic percent of fluorine.
 2. A top emissionorganic electroluminescent device according to claim 1, wherein the SiNlayer contains 29 to 40 atomic percent of silicon.
 3. A top emissionorganic electroluminescent device comprising: a substrate; a layeredstructure disposed on the substrate, said layered structure includes afirst electrode, a second electrode, and an organic layer disposedbetween said first electrode and said second electrode, and a protectivelayer disposed closer to a light extraction side than said layeredstructure; wherein the protective layer contains silicon, nitrogen, 10to 50 atomic percent of hydrogen, and 0.01 to 1 atomic percent offluorine.
 4. A top emission organic electroluminescent device accordingto claim 3, wherein the protective layer contains 29 to 40 atomicpercent of silicon.